Outburst Flood - Definition and Classification

Definition and Classification

Megafloods are paleofloods (past floods) that involved rates of water flow larger than those in the historical record. They are studied through the sedimentary deposits and the erosional and constructional landforms that individual megafloods have created. Floods that are known to us through historical descriptions are mostly related to meteorological events, such as heavy rains, rapid melting of snowpacks, or combination of these. In the geological past of the Earth, however, geological research has shown that much larger events have occurred. In the case of outburst floods, such floods are typically linked to the collapse of the barrier forming a lake. They fall in the following classification according to the mechanism responsible:

• Collapse of glacier dams that impound proglacial lakes (Missoula Floods).
• Rapid erosion, melting of ice sheets (jökulhlaups).
• Collapse of earthen barriers (landslides or glacial moraines).
• Collapse of volcanic dams created by lava flows, lahars, or pyroclastic flows.
• Overtopping of earthen or rock barriers
  • Lake overtopping (e.g., Lake Bonneville).
  • Ocean spilling over a dividing ridge into a landlocked basin (e.g., Zanclean flood, Black Sea flood). A smaller scale example would be the Pantai Remis landslide.